1. Field of the Invention
The present invention relates to a reproducing apparatus, and more particularly to an equalizing process for a reproduced information signal.
2. Description of Related Art
Heretofore, there have been known digital VTRs (video tape recorders) arranged to convert a video signal or an audio signal into a digital signal, to record the digital signal on a magnetic tape and to reproduce the digital signal from the magnetic tape. In the digital VTRs, a reproduced signal is subjected to an equalizing process by an equalizer so as to compensate for the deterioration of a signal occurring in a recording and reproducing system, the unevenness of characteristics due to the variety of kinds of tapes, etc. By this process, it is possible to obtain a reproduced signal having few errors.
In addition, there has been known a technical art of controlling the equalizing characteristic of an equalizer on the basis of an error rate in a reproduced signal.
The above-mentioned method of controlling the equalizing characteristic on the basis of an error rate is effective. However, in such a state that there are very few errors with an error rate lowered, the influence of a dropout due to the defect of a tape would become more dominant in the proportion of errors than the influence of the equalizing characteristic of an equalizer.
Therefore, in a case where the equalizing characteristic has been controlled merely on the basis of an error rate obtained for a given period of time, the equalizing characteristic would be changed on the basis of an error due to the dropout, so that there is a possibility that the equalizing characteristic is deteriorated instead of being improved.
In order to avoid such an inconvenience, it is necessary to obtain an error rate by counting up errors for a long period of time up to such a degree that a local increase of the number of errors due to the dropout becomes negligible. Accordingly, it would take a long period of time to obtain an optimum equalizing characteristic.
On the other hand, in the so-called wobbling method in which an optimum equalizing characteristic is sought by varying the equalizing characteristic, although such a direction as to make errors fewer as compared with the present status can be found, a direction in which an optimum point for the equalizing characteristic is located cannot be found. Therefore, according to the wobbling method, there is a possibility that the equalizing characteristic is controlled to a value which does not correspond to the optimum point, although it corresponds to a minimum point for errors.